1. Field of the Invention
The present invention relates to a communication apparatus having a function of receiving a calling party number through a network, and a communication method using the same.
2. Prior Art
Upon reception of an incoming call from an integrated service digital network (ISDN) line, a conventional private branch exchange (PBX) connected to an ISDN directly transmits calling party number information to an ISDN extension terminal. Some conventional ISDN terminals have the following function. Upon reception of an incoming call from an ISDN line, this terminal stores calling party number information. When speech communication is completed, and an outgoing call is to be generated with respect to the calling party of the speech communication, the terminal reads out the calling party number from the memory and generates an outgoing call to the calling party of the number.
FIG. 8 shows the arrangement of a conventional PBX. FIG. 9 is a flow chart showing a terminating sequence employed by the PBX.
Referring to FIG. 8, a PBX 603 accommodates an ISDN line 602 as a trunk and is connected to an ISDN 601. A terminal 604 is an ISDN extension terminal of the PBX 603. A basic rate trunk (BRT) 605 is connected to the ISDN line 602 and detects an incoming call to the PBX 603 received via the ISDN 601. A basic rate interface (BRI) 606 is connected to the extension terminal 604 and performs originating/terminating control of the terminal 604. A time switch (TSW) 607 performs connection of a speech channel. A conventional communication controller (CCC) 608 controls the overall PBX 603. When, for example, an incoming call is received, the CCC 608 determines a called party extension, and instructs the BRI 606 to connect the incoming call to the terminal 604 of the called party. Control signals are exchanged between the CCC 608 and the BRT 605, the CCC 608 and the BRI 606, the CCC 608 and the TSW 607, and the like through a control line 609.
In the arrangement shown in FIG. 8, terminating control of an incoming call to the terminal 604 received via the ISDN 601 is performed by the PBX 603 in accordance with the sequence of the flow chart shown in FIG. 9.
When a "set-up" message is sent from the ISDN 601 to the PBX 603 through the ISDN line 602, the BRT 605 detects reception of an incoming call (step S71). Assume that the "set-up" message includes calling party number information, and that a calling party number is the telephone number of the calling party. In this case, assume that the calling number is 037582414. The BRT 605 acknowledges detection of an incoming call to the CCC 608 through the control line 609.
Upon reception of the acknowledgement of an incoming call, the CCC 608 determines an extension as a called party according to a known response scheme (step S72).
Upon recognizing that the called party extension is the extension terminal 604, the CCC 608 instructs the BRI 606 through the control line 609 to connect the incoming call to the extension terminal 604 (step S73).
Upon reception of the connection instruction from the CCC 608, the BRI 606 connects the incoming call to the extension terminal 604 (step S74).
Upon reception of the incoming call, the extension terminal 604 stores the calling party number included in the "set-up" message and displays it on the display. In this case, the calling party number is 037582414.
When the terminating sequence is completed, a corresponding speech line is connected by the TSW 607, and speech communication starts. After the speech communication is completed, the operator can generate an outgoing call from the extension terminal 604 to the calling party of the trunk number "037582414", i.e., the calling party of the previous speech communication, with a simple operation. Whether an extension terminal uses an extension or a trunk to communicate with another party is predetermined, unless otherwise indicated. Such information is called a calling mode. That is, if the calling mode of the extension terminal 604 designates a trunk, the terminal reads out the calling party number stored in step S74, and generates an outgoing call to the party of the read number in accordance with the operation performed by the operator.
According to the conventional sequence, however, if the calling mode of the extension terminal 604 designates an extension, the use of the calling party number "037582414" for the trunk, stored in the memory, leads to an originating error.